Wavelength or frequency Intensity Location/position of source Reflects off some materials Refracted (bent) moving through other materials
Eyes categorize wavelength into relative intensities within wavelength bands RGB ~ Red, Green, Blue Long, medium, short wavelengths Color is a neural/psychological construct
Cornea - refraction (2/3 of total) Pupil - light intensity; diameter regulated by the Iris. Lens - refraction (remaining 1/3; variable focus)
Retina - light detection ~ skin or organ of Corti Pigment epithelium - regenerate photopigment Muscles - move eye, reshape lens, change pupil diameter
Image inverted (up/down) Image reverseed (left/right) Point-to-point map (retinotopic) Binocular and monocular zones
Central 1-2 deg of visual field ~ thumbnail @ arm’s length Aligned with visual axis; center of gaze Retinal ganglion cells pushed aside Highest acuity vision == best for details
Outer segment Membrane disks Photopigments Sense light, trigger chemical cascade Inner segment Synaptic terminal Light hyperpolarizes photoreceptor! The dark current
Physiologically backwards Dark current (more NT released in dark) Anatomically inside-out Photoreceptors at back of eye
Center region Excites (or inhibits) Surround region Does the opposite Bipolar cells & Retinal Ganglion cells -> Most activated by “donuts” of light/dark Local contrast (light/dark differences)
Black vs. white (achromatic) Long ( red) vs. Medium ( green) wavelength cones (Long + Medium) vs. Short ( blue) cones Can’t really see reddish-green or bluish-yellow